The major rivers of the Fraser, Harrison and Pitt, as well as their valley corridors, provided Stó:lō peoples with trade access via canoes and trails. The Stó:lō people also had access to areas by ocean routes that allowed them to traverse both to the Sunshine Coast and to Vancouver Island. Many contemporary roads and highways are based on traditional native paths that often developed out of existing animal trails. The first epidemics of smallpox affected Stó:lō communities even before contact with Europeans, because of native peoples traveling the extensive trading networks of trails and spreading the disease.